C#组合算法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class Default15 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

        int[] el = { 1, 2, 3, 4,5};
      
    

       this.Response.Write(GetCom<int>(el, 3));
    }

    public string  GetCom<T>(T[] el, int n)
    {
        string s = "";
        int p = 0;
        int m = el.Length;
        int[] flags = new int[m];
        string str = "";

        for (int i = 0; i < n; i++)
        {
            flags[i] = 1;
        }

        for (int i = n; i < m; i++)
        {
            flags[i] = 0;
        }

        p = 0;
        for (int i = 0; i < flags.Length; i++)
        {
            if (flags[i] == 1)
            {
                p++;
                string t = "";
                if (p < n)
                {
                    t = ",";
                }
                s += el[i].ToString()+t;
            }
            str += flags[i].ToString();
        }
        str += ";";

        s = s + "<br/>";
        int count = 1;

        bool has10 = false; //是否有"10"组合的标志:true-有;false-无

        int bound = 0; //第一个"10"组合的索引

        int num1 = 0;           //"10"组合左边的"1"的个数
        int j;

        while (true)
        {
            num1 = 0;

            has10 = false;

            for (int i = 0; i < m - 1; i++)
            {
                if (flags[i] == 1 && flags[i + 1] == 0)//找到第一个"10"组合
                {

                    bound = i;

 

                    flags[i] = 0;//将该"10"组合变为"01"组合

                    flags[i + 1] = 1;

 

                    for (j = 0; j < num1; j++)//将其左边的所有"1"全部移动到数组的最左端
                    {

                        flags[j] = 1;

                    }

                    for (j = num1; j < bound; j++)
                    {

                        flags[j] = 0;

                    }

 

                    has10 = true;

                    break;

                }

                else if (flags[i] == 1)
                {

                    num1++;

                }
               

            }
            if (has10 == false)//没有"10"组合了,代表组合计算完毕

            {
                break;
            }
            else
            {
                count++;
            }
            p = 0;
            for (int i = 0; i < flags.Length; i++)
            {
                if (flags[i] == 1)
                {
                    p++;
                    string t = "";
                    if (p < n)
                    {
                        t = ",";
                    }
                    s += el[i].ToString() + t;
                }
                str += flags[i].ToString();
            }
            str += ";";

            s = s + "<br/>";
        }

        string[] sa = str.Split(';');
        str ="";
        Array.Sort(sa);

        for (int i = sa.Length-1; i >0 ; i--)
        {
            string tempS = "";
            if (i > 1)
            {
                tempS = ";";
            }
            str += sa[i] + tempS;
        }

        /*重新排序*/

        string[] numA = str.Split(';');
        string tempnum = "";
        foreach (string ss in numA)
        {
           
            for (int jj=0;jj<ss.Length; jj++)
            {
                if (ss[jj] == '1')
                {
                    tempnum += el[jj].ToString() + ",";
                }
            }
            tempnum +=  "<br/>";
        }

        return tempnum;

    }
}